Binge Eating Disorder (BED) is arguably the most common eating disorder and is associated with high levels of psychological distress and obesity. The psychological aspects of BED have been better studied than the biological aspects, and reveal that stress and hunger are two common binge antecedents. The aim of this proposal is to examine the psychophysiological effects of stress, focusing on the potential mediating role of cortisol and ghrelin in stimulating food intake in BED, which may help maintain the disorder. This topic fits well with The NIH Obesity and Eating Disorders Program's emphasis of investigator-initiated basic and clinical research relating to biomedical and behavioral aspects of obesity and eating disorders. The approach will be to use a laboratory-based social stress protocol, the Trier Social Stress Test in 18 obese BED and 18 obese nonBED subjects, equally divided by gender, and examine plasma cortisol and ghrelin levels in both groups. A secondary aim is to analyze the effects of the stressor on other psychological factors, including changes in subjective stress, mood, and anxiety. Post stress effects will also be monitored in the following 24 hours by records of food intake, mood, hunger, and levels of 24-hour urinary cortisol. This study aims to assess how stress influences key biolological and psychological factors during the evening, the time when binge eating occurs most frequently. One key hypothesis is that stress mediates binge eating through an enhanced cortisol and gherlin response, which concurrently stimulates hunger and greater meal intake. This integrated research design of laboratory-based and daily diary data collection aims to reveal potential biological and psychological maintenance factors of BED, which are essential for developing effective treatments. The study is also interdisciplinary, thus fulfilling the new NIH roadmap review criteria.